In gynecology and obstetrics, the simultaneous assessment of the fetal heart rate (FHR) and uterus activity (TOCO) are usually the main parameters used to determine the fetal condition. Monitors, known as fetal monitors or cardiotocographs (CTG monitors) are used for measuring and recording both these parameters.
Establishing a diagnosis on the basis of information provided by the CTG, is a critical and sensitive process. The fetal heart rate trace, for example, may contain a multiplicity of different patterns. The diagnostic meaning of these patterns depends on their frequency and their spectral components, that is, a certain pattern in a given range may have another meaning if it appears in another spectral range. The interrelation between the FHR trace and the TOCO channel and the degree of events is also significant for correctly diagnosing a fetal condition. The assessment of the CTG is very sensitive to misinterpretation. A false or incomplete diagnosis may seriously endanger the fetus and/or the mother.
In order to prevent against the serious consequences of CTG misinterpretation, there have been several attempts to "formalize" the process of CTG interpretation. So-called "score tables" list several criteria or patterns which may appear in the CTG and assign a "score" or "points" (usually, an integer or a natural number) to listed criteria or patterns. By addition of the single scores, one obtains a "sum-score". A reference table relates the "sum-score" directly to the diagnostic assessment. For example, in one system which scores within a range of 0-25 with higher scores indicating progressively more critical situations, a sum-score equal to or exceeding 10 may be classified as "pathologic", indicating high danger for the fetus. A sum-score equal to or exceeding 6 may be classified as "prepathologic", indicating that increased attention is necessary and a sum-score below 4 is classed as "normal".
There have already been attempts in the prior art to automate the process of CTG scoring. However, none of these systems has proven particularly successful. CTG interpretation systems already available on the market are restricted to the calculation of the fetal heart rate variability, special indices or factory-defined scores. The calculated variability, indices and scores do not match the well-known score tables hitherto used for manual CTG evaluation.
U.S. Pat. No. 5,442,940 to Secker et al. describes apparatus and a method for evaluating a fetal condition which allows the individual physician to "edit" and "modify" the rules controlling the operation of the apparatus. Allowing the physician to change the rules, does not allow for a consistent set of rules. Though the above method indicates an alarm situation, it does not specify the reasons causing the alarm. Further, though Secker indicates a net "score", he does not detail the breakdown and computation for this score.
The Sonicaid System 8000 manufactured by Oxford Sonicaid Ltd. of West Sussex. England is a stand-alone system for monitoring the fetal condition of the at-risk pregnancy. The system analyzes key CTG parameters and displays a graph and recordings of up to one hours data. The system does not continuously record and is limited to recording one fetal sensor at a time.
None of the prior art systems permit the simultaneous connection of a plurality of fetal monitors nor do they allow for the connection of any type of fetal monitor, regardless of manufacture.